This invention relates to a machining fluid of water soluble type which employs organic substances as its principal ingredients.
Conventional machining fluids for use in metal machining operations such as cutting, grinding, drawing and rolling are classified roughly into water-insoluble machining oils and water-soluble machining fluids. The water-insoluble machining oils which are prepared by using petroleum products as their fundamental materials have a long history, but a recent trend in many fields of industries is to replace machining oils of this type by water-soluble machining fluids. The primary reason for this trend is an increasing fear of fire accidents accompanying a great increase in the consumption of machining oils with the progress of enlargement, automation and speed-up of the metal machining equipment and the employment of severe machining conditions. Subsidiary reasons include the importance of saving of petroleum resources and increasing costs of petroleum products.
Conventional water-soluble machining fluids are synthetic fluids prepared by using water soluble or solubilized surface-active agents and auxiliary synthetic materials with the addition of rust-inhibitors, oilness improvers, extreme pressure additives and/or antiseptic agents for example. As specified in JIS (Japanese Industrial Standard) K-2525, water soluble machining fluids are classified into the following three classes.
Class W1: Water soluble machining fluid of emulsion type. (Diluted fluid for practical use becomes milk-white emulsion.) PA0 Class W2: Water soluble machining fluid of solubilized type. (Main ingredients including surface-active agents are organic substances: diluted fluid for practical use becomes a transparent or semitransparent and water soluble liquid.) PA0 Class W3: Water soluble machining fluid of solution type. (Main ingredients are inorganic salts: diluted fluid for practical use becomes a chemical solution.)
These machining fluids are economical and free from the fear of causing fire accidents. However, there are some problems almost common to conventional machining fluids of water soluble type. The first problem is undesirable influences of the machining fluids, which are inevitably scattered as mist, on the health of the workers. For example, Class W3 machining fluids which are recently prevailing contain nitrites as the principal component together with auxiliary components such as benzoates, borates, molybdates and primary, secondary or tertiary amines. Among these ingredients, the nitrites combine with the amines to form nitroso compounds which are strongly suspicious as cancerogenic as described in many scientific reports. Besides, it is reported that absorption of benzoates, borates or molybdates jointly with amines becomes a cause of various chronic diseases and even of cancers.
As another problem of water soluble machining fluids composed mainly of inorganic salts, it is difficult to appropriately dispose of the waste fluids, and the waste fluids discharged from the machining facilities, even after some treatment, are liable to cause water pollution. As will readily be understood, the waste fluids discharged into streams or lakes cause significant increases in the inorganic salt concentrations in the waters. Furthermore, the waste fluids exhibit considerably high values of COD (chemical oxygen demand) that are not easy to lower and therefore exert detrimental influences on the microorganisms in natural waters. Besides, sulfur compounds, chlorine compounds and/or phosphorus compounds that are contained in conventional machining fluids of water soluble type to serve as extreme pressure additives place significant restrictions on the applicability of the machining fluids to some metals and, moreover, become a cause of air pollution even after troublesome treatment of the waste machining fluids.